" Which physical property is lower for alkaline earth metals as compared to alkali metals of the same period ?

Explain why alkaline earth metals are harder than alkali metals ?

Compared with alkaline earth metals, the alkali metals exhibit

Compared with the alkaline earth metals, the alkali metals exhibit

Assertion (A): Alkaline earth metals are harder than alkali meatals. Reason (R ): Atomic radii of alkaline earth metas are smaller thant the corresponding alkali metals in the same period.

The correct reason for smaller size of alkaline earth metals than that of alkali metal is that